They would act depressed. That's so sad why would you want to break anythings spirit, and plus that's what is sooooo amazing about horses is their spirits! That's why they are so beautiful, free spirited.
Is Abby like this or does she still have hers intact. Have you looked into liberty training? That could bring any horse with a broken spirit back into the world.
Here is a video of Carolyn Resnick, she has tons more. Im starting to train my mare this way and just by changing my whole approuch with Gypsys training, man I can see a huge change in her whole attitude.
I love this quote... "If he'll give me time I'll let him be what ever he wants to be"
That is brilliant and every rider needs to take those words to heart!